cpufreq: speedstep-lib: make several arrays static, makes code smaller

Don't populate arrays on the stack, instead make them static.
Makes the object code smaller by over 860 bytes:

Before:
   text	   data	    bss	    dec	    hex	filename
  10716	   5196	      0	  15912	   3e28	drivers/cpufreq/speedstep-lib.o

After:
   text	   data	    bss	    dec	    hex	filename
   9690	   5356	      0	  15046	   3ac6	drivers/cpufreq/speedstep-lib.o

Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>